Patent GB-628469-A (GB)
Title: Control mechanism for internal combustion engines
IPC: F02D9/00
Filed: 1946-05-16
Abstract: 628,469. Fluid-pressure servomotor-control systems. BENDIX AVIATION CORPORATION. May 16, 1946, No. 14830. Convention date, June 11, 1945. [Class 135] [Also in Group XXIV] In automatic boost control mechanism for internal combustion engines of the kind in which the throttle valve is adjusted by manual control means and also by fluidoperated servo means under the control of a valve adjusted jointly by the manual control means and by a member responsive to the induction pipe pressure, several control members are provided, each adjusting the datum of the servo means according to a different predetermined programme and control means responsive to an engine operating condition are also provided whereby when one of the control members is rendered effective or ineffective, one of the other control members automatically becomes correspondingly ineffective or effective without direct operation by the control means. Thus a programme giving the highest pressures is operative if the water injection system is working but if not, one of two other pressureselection programmes is operative depending on whether the change speed gear of the supercharger is in high or low gear. The complete mechanism is housed in a casing 7, Figs. 2 and 7 and controls the throttle valve 19 of an aircraft engine in accordance with the pressure in the intake manifold 20 on the engine side of a supercharger 23 driven by the engine 24 through a change-speed gear or a hydraulic coupling 26. The mechanism is shown diagrammatically in Fig. 6 and includes a pilot's hand lever 1 connected directly to the throttle 19 through a linkage 3, 5, a shaft 6 bearing a crank-pin 11, a floating lever 12, a link 13, a bell-crank 15, a shaft 16 and a linkage 17, 18. Movement of the shaft 6 is limited by a stop 9 engaged by an arm 10 and an adjustable screw 9a. The floating lever 12 is also connected through a link 75 with a spring-pressed servo-piston 68 under the control of a piston valve 56, itself actuated by a pressure-responsive mechanism 53 through links 52, 54 connected to a floating lever 50. The mechanism 53 comprises two opposed bellows 76, 77 with fixed outer ends 79, 84 and a common movable head 82 connected to the link 52. The bellows 77 is partly evacuated and contains a spring 78. The bellows 76 is open to the manifold pressure through a pipe 81 and a passage 80 in the casing 7. Excessive expansion of the bellows 76 and contraction of the bellows 77 is prevented by a rod 176 whilst an adjustable rod 174 inhibits further automatic opening of the throttle below a critical manifold pressure. The pressure setting or datum of the mechanism 53 is adjustable in accordance with two or more predetermined programmes or schedules by adjustment of the lower pivot 49 of the floating lever 50 through cam and lever mechanism operated from the pilot's lever 1 through the shaft 6 and a linkage 8, 30, 31. As shown, the arm 31 of the linkage operates a shaft 32 bearing three cams 33, 34, 35 engaging lateral followers 40, 41 projecting from levers 85, 86, 87, Figs. 6 and 10, rotatably mounted on a shaft 43. The levers 85, 86, 87 are pressed against or toward the cams by spring fingers 98, 99, 100, forming part of a spring plate 101 secured to the casing 7. Also mounted on the shaft 43 is a lever or frame 42 comprising end portions 88, 89 and horizontal portions 90, 91. The lever 42 is biassed in a counter-clockwise direction by a spring 44 weaker than the springs 98, 99, 101 and the cross-bar 90 carries adjustable screws 95, 96, 97 which engage the ends of the cam follower levers 85, 86, 87. Clockwise movement of the lever 42 which is connected by a member 48 to the lever 50 corresponds to an increased pressure setting of the mechanism 53 and thus the cam 35 with the lowest rise gives the highest pressure setting. Cam 34 having the highest rise gives the lowest pressure setting, whilst cam 33 gives an intermediate setting. Either or both of the follower levers 85, 87 may be moved out of operative relation with its respective cam by rods 120, 110 respectively actuated by pistons 121, 111 with restricted escape orifices 127, 118. The piston 121 is moved to the left, Fig. 6, to disengage the lever 85 under the pressure of hydraulic fluid in a pipe 124 when a valve 125 controlling a servopiston 163 which actuates the change-speed gear 26 moves to place the gear in the high ratio position. The valve 125 may be operated manually from the pilot's cabin by a rod 170 or automatically by a bellows responsive to atmospheric pressure. In the latter case the gear 26 is moved over to the high-speed ratio at a predetermined low atmospheric pressure and the piston is moved to render the camfollower lever 85 ineffective. If the supplementary water injection system is inoperative and the high-speed ratio is effective, the middle cam 34 becomes the operative cam and this adjusts the pressure setting in accordance with the lowest pressure setting programme. Similarly, the cam 35 can be rendered ineffective by the piston 111 when the supplementary water injection system is inoperative. In this case the cam 33 or 34 becomes effective according as the gear 26 is in low or highspeed ratio. Normally the water injection system is inoperative and the piston 111 is maintained in the left-hand position, Fig. 6, by oil or other fluid pressure in conduits 115, 113. When the water injection system is operative, the pressure therein operates through a conduit 146 on a diaphragm 155, Figs. 3 and 6, to close a valve 151 normally held open by a spring 153. The valve 151 cuts-off the conduit thus allowing the conduit 113 to vent through the orifice 118. Under these circumstances the cam 35 takes charge over either of the cams 33, 34 and the bellows mechanism 53 is adjusted according to the highest pressure setting programme. The movement of the levers 85, 86 in the pressure increasing direction is limited by adjustable screw-threaded rods 128, 130 supported in the end wall of the casing 7 and accessible on removal of a cover 132. The ends of the shaft 43 and of the spring plate 101 are supported by a bracket plate 104, bolted inside the casing 7. The floating lever 50, Figs. 6 and 9 (see Group XXIV), comprises side plates 187, 188 and a central block 191 slidable against the action of a spring 196. The block 191 is adjusted by a screw 197 mounted at an angle in the block and contacting the inclined surface of an ear 200 on the side plate 187. Thus the screw 197 adjusts the pressureadjusting range of the bellows mechanism 53 whilst the screws 95, 96, 97 adjust the pressure settings of the respective cams 33, 34, 35 in relation to one another. The water injection system comprises a source 139 of water, wateralcohol, or other supplemental fluid forced by a pump 140 with a byepass relief valve 145 through a conduit 138 and a metering device 137 to the main fuel nozzle 135 supplied from the carburetter 27. The conduit 138 contains a valve 141 opened by an electromagnet when a switch 143 is closed. The conduit 146 to the diaphragm 155 branches from the conduit 138. When the pilot's lever 1 is moved beyond a predetermined position an arm 177 of the bell-crank 15 acts on a pin 181 carried by a lever 178 which through a pin 184 restores the control valve 56 to its netural position so that the throttle is then operated entirely manually. The lever 178 is normally biassed against a stop 186 by a spring 185. The casing 7 is in three convenient sections B, C, D secured by bolts 201, 203. Specification 603,157 is referred to.